Built on success in evaluating the wheat germ-expressed Pfs230 domains, recombinant Pfs230 domains were expressed in P. pastoris and E. coli, where antisera raised against specific domains demonstrated potent transmission blocking activities in an ex vivo standard membrane feeding assay, in a complement-dependent manner. Multiple expression clones were evaluated for their recombinant Pfs230 production yield and induction of functional antibodies. A Pichia expression clone was selected, and cGMP grade recombinant Pfs230 was manufactured, followed by generation of cGMP grade Pfs230-EPA and Pfs230-EPA/Alhydrogel vaccine. This drug product passed FDA scrutiny, and during FY2015 was combined with Pfs25-EPA/Alhydrogel in order to be tested in humans as a potentially effective combination transmission blocking vaccine that improves upon Pfs25-EPA/Alhydrogel alone. To date, the combination vaccine has been administered to volunteers in the US, where it has been found to be safe, and 2 doses have been given to volunteers in Mali, where it has thus far proven to be safe. A third dose is planned for Sept 2015, and a 4th dose in Sept 2016, after each of which dose antibodies will be assessed by ELISA for titer, and by feeding assays for functional activity.

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Wu, Yimin; Sinden, Robert E; Churcher, Thomas S et al. (2015) Development of malaria transmission-blocking vaccines: from concept to product. Adv Parasitol 89:109-52